Grapevine ESCA disease, black dead arm disease, and Eutypa dieback disease (hereinafter may also be simply referred to as the subject diseases) are diseases which mainly occur in Europe, and known as major three diseases of grapevine trunk diseases in Europe.
Among the three diseases, the area where ESCA disease occurs is the largest, and ESCA disease is particularly regarded as a problem. On the other hand, recently, the area suffering from black dead arm disease has been rapidly expanding, bringing about a problem.
As to grapevine ESCA disease, it is believed that after the initial infection by Phaeomoniella chlamydospora or Phaeoacremonium aleophilum, one of wood-decay fungi such as Fomitiporia punctata, F. mediterranea, or Stereum hirsutum enters into the trunk from the infected site. As the decaying at the pathogen entry site, the discoloration and sponge-like formation of the vascular bundle, or the like gradually proceeds, the branches and leaves are supplied with less water and nutrients, eventually leading to the onset of symptoms such as leaf discoloration, dieback, and low fruiting. Thus, the grape production is significantly lowered. Grapevine ESCA disease is different from general diseases in that the ESCA disease onset is often seen in trees particularly grown to some extent for ten or more years. Since grape trees of ten or more years old can produce grapes having favorable taste, the economical damage, if any, to the producers could be great. Although sodium arsenite has been used as an effective chemical against the subject diseases, the use has been banned in many countries because of the toxicity problems to human, animals, and the environment. There is no effective measure at present.
The grapevine ESCA disease symptoms often appear after the decaying at the pathogen entry site inside the trunk gradually proceeds. In addition, except for several branches, all the other branches of a grape are cut off in winter. Accordingly, if a trunk portion near the remaining branches is infected with grapevine ESCA disease, the symptoms such as dieback and leaf discoloration are observed from the grape in the next year. Meanwhile, if the trunk portion near the remaining branches is not infected with grapevine ESCA disease, the symptoms may not appear in the grape in the next year. For these reasons, to identify a grape infected with grapevine ESCA disease, a follow-up examination is required for a long period, specifically at least three years.
Grapevine black dead arm disease is a new disease whose damage has become noticeable since this century. Botryosphaeria parva causes this disease. At the initial infection, a yellowish orange spot is observed like downy mildew, then leading to necrosis. This results in considerable influences on the grape production.
Grapevine Eutypa dieback disease is caused by Eutypa lata. The hypha growth rate of Eutypa lata is slow, but the grape growth is gradually retarded after the infection as in the case of ESCA disease, so that the production is significantly lowered. Although control is performed such as a microbicide treatment on the cross sections of branches after the pruning or incineration of damaged plants, only a limited effect is obtained.
Patent Literature 1 states that a plant disease control agent containing a biocidal inorganic compound, an amphoteric surfactant, and a nonionic surfactant and/or an anionic surfactant exhibits a control effect against a plant disease, specifically cucumber powdery mildew. However, there is no description or suggestion at all regarding grapevine ESCA disease.
Patent Literature 2 discloses that an agent for increasing a sugar content in a fruit of a plant, containing a compound represented by the formula MX (M represents alkali metal ion or alkaline earth metal ion, and X represents carbonate ion, hydrogen carbonate ion, acetate ion, citrate ion, succinate ion, phosphate ion, or pyrophosphate ion) as an active ingredient, remarkably increases the sugar content in a fruit of a plant, for example. However, there is no description at all regarding the control agent and the control method against the subject diseases.
Patent Literature 3 discloses a method for controlling grapevine ESCA disease by using an inhibitor of mitochondrial breathing chain at the level of b/c1 complex of plant pathogens. However, there is no description at all regarding the control agent of the present invention. Meanwhile, the control effect against grapevine ESCA disease is evaluated by examining the disease severity of shoots at each of four sub-stages of the growth stage. However, there is no description of the evaluation method of the present invention.
Patent Literature 4 describes a composition containing potassium hydrogen carbonate and an active ingredient selected from boscalid, pyrimethanil, metrafenone, cyprodinil, and fludioxinil. However, the control effect against the subject diseases is not demonstrated at all.